1. Field of the Invention
The present invention relates to a method for producing an ink jet recording head which discharges ink to record on a recording medium, an ink jet recording head, and a substrate for an ink jet recording head.
2. Description of the Related Art
There has been conventionally known an ink jet recording head (hereinafter simply referred to as “recording head”) which discharges ink as ink droplets through discharge ports while subjecting the ink to thermal energy. Sectional views of FIGS. 1A and 1B illustrate a general recording head of this kind. In FIGS. 1A and 1B, the recording head 150 has an orifice plate 105 on which a plurality of discharge ports 107 are formed for discharging ink, and a substrate 101 on which energy generating elements (not shown) are formed for applying thermal energy to the ink. The substrate 101 has ink flow paths 106 for supplying the ink to a plurality of the discharge ports 107, and a common liquid chamber 108 for supplying liquid to the ink flow paths 106. To dispose the common liquid chamber 108 in the substrate 101 it is necessary to form an ink supply port 110 on a surface opposed to a surface (an obverse surface of the substrate) on which the energy generating elements are formed. Moreover, as disclosed in U.S. Pat. No. 6,137,510, reinforcing ribs may be, though not shown in FIG. 1, disposed at a center portion of the orifice plate 105 in the longitudinal direction so as to correspond to the ink supply port 110.
As a method of forming an ink supply port in the recording head shown in FIG. 1, there have been known a method using an anisotropic etching technique disclosed in U.S. Pat. No. 6,139,761, and a method for mechanically forming an aperture using sandblasting and drilling and the like. Among these methods, using an anisotropic etching technique is an excellent method because it has the following advantages:
(1) The ink supply port can be precisely formed compared with the other methods (Particularly in U.S. Pat. No. 6,139,761, since the method disclosed forms the ink supply port after the flow path shaping member such as the orifice plate is formed, the position relationship between the discharge ports or the ink flow paths and the supplying ports can be made very precise).
(2) It is capable of dealing with various kinds of ink since the formed surface of the wall is alkali-resistant.
In order to improve the accuracy of an opening of the ink supply port on a side of an obverse surface of the substrate when using the above method, a method for producing an ink jet head is disclosed in U.S. Pat. No. 6,143,190 in which an embedded dummy layer is disposed in a silicon substrate.
The above-mentioned method for producing an ink jet recording head is a very excellent method, hence is in practical use; however, in the recording head shown in FIG. 1, the more the number of the discharge ports 107, the longer the silicon substrate 101. In thus produced elongated ink jet recording head comprising a multitude of discharge ports arranged in a line for discharging ink (hereinafter simply referred to as “elongated head”), a single elongated ink supplying port 110 is disposed in the silicon substrate 101 at its center portion, which unfavorably reduces its mechanical strength. Such a problem occurs similarly in the case of reducing the size of the silicon substrate 101 for the purpose of cutting the producing cost; namely, the smaller the substrate, the less its mechanical strength.
The reduction of the mechanical strength of the silicon substrate causes the silicon substrate 101 to be relatively easily deformed. If such an elongated head is produced using the conventional producing method as it is, the deformation of the substrate possibly causes problems that the orifice plate 105 is unstuck from the silicon substrate 101, or the orifice plate 105 is deformed. Accordingly, the deformation of the orifice plate 105 causes the discharge ports 107 formed on the orifice plate 105 to be out of alignment in its position and opening direction, which also may reduce the recording quality. Moreover, using the silicon substrate 101 having reduced mechanical strength increases the likelihood that the silicon substrate 101 is unfavorably damaged in its producing process, which may cause reduction of the production yield.
Consequently, the inventors have made an investigation to improve the mechanical strength of the silicon substrate by a method as simple as possible, but there is concern that simply dividing the ink supply port into plural number of ink supply ports and disposing beams therebetween may possibly decrease the opening area on the obverse surface of the substrate due to the characteristic of anisotropic etching, and causes the ink supplying characteristic to be fluctuated according to the ink flow paths.